Technical Field
The present invention relates to a combustion system including an ion transport membrane assembly coupled to an internal combustion engine to generate power via oxy-combusting a fuel stream. The present invention further relates to a method of combusting a fuel stream via the combustion system.
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Energy consumptions continue to rise, thus producing more emissions of CO2 [Olajire AA, CO2 capture and separation technologies for end-of-pipe applications—a review, Energy, 2010, 35, 2610-2628]. Carbon capture from point source emissions has been recognized as one of several strategies necessary for mitigating the unfettered release of greenhouse gases (GHGs) into the atmosphere. To keep GHGs at manageable levels, a drastic reduction in CO2 emissions may be needed through capturing and separation [Perry S, Klemeš J, Bulatov 1. Integrating waste and renewable energy to reduce the carbon footprint of locally integrated energy sectors, Energy, 2008, 33, 1489-1497]. World population growth and the consequent rise in pollution and greenhouse gases emissions are among the challenging problems that the scientific community must solve in the near future [Amelio M, Morrone P, Gallucci F, Basile A. Integrated gasification gas combined cycle plant with membrane reactors: Technological and economical analysis, Energy Conversion and Management, 2007, 48, 2680-2693]. The energy production from fossil fuel sources represents a large portion (about 65%) of the total greenhouse gases emissions (carbon dioxide CO2, methane CH4 and nitrogen oxide N2O) [Cumo M, Santi F, Simboletti G. Energia, cambiamenti climaticie sequestro dell'anidride carbonica, La Termotecnica, 2003, 33-43]. Besides, mobile sources such as internal combustion engines represent more than 25% of the total CO2 emissions. Most scientists agree that there is a strong connection between climate change and the anthropogenic emissions of greenhouse gases, of which CO2 is by far the most important gas in terms of the amount emitted. Carbon dioxide is the major atmospheric contaminant leading to a temperature increase due to the greenhouse effect. The scientific community considers the anthropogenic CO2 emission needed to maintain the existing world climate condition. As a result, radical changes in fossil fuel-operated technologies are needed.
Oxy-combustion is among one of the most promising carbon capture technologies. Accordingly, a hydrocarbon fuel is burned in a nearly pure oxygen atmosphere, or in a nitrogen-free atmosphere. In view of that, the products of the combustion consist of a mixture of only carbon dioxide and water vapor [Nemitallah, M. A Habib, M. A., Ben-mansour, R., Ghoniem, A. F., Design of an ion transport membrane reactor for gas turbine combustion application, Journal of membrane science, 2014, 450, 60-71]. Water vapor can easily be condensed and the resulting carbon dioxide can be captured for industrial purposes, or it can be stored. Although this technology is applicable to conventional combustion systems it needs an oxygen-separating system, wherein oxygen is separated from air or another oxygen-containing stream. Having an oxygen-separating system as a separate unit for removing undesired substances in oxy-combustion consumes a portion of the output power generated by the combustion system [Haslbeck, J., Capicotto, P., Juehn, N., Lewis, E Rutkowski, M., Woods, M., et al., bituminous coal to electricity, Washington D.C., DOE/NETL-1291, 2007]. Therefore, utilizing the oxygen-separating system in a combustion system is not an efficient way to turn a combustion system into an oxy-combustion system.
A new approach for oxy-combusting a fuel has been recently disclosed via the use of ion transport membrane reactors (OTMR). In these reactors, oxygen is separated from a gaseous mixture (generally air) at a temperature ranging from 650° C. to 950° C., and a fuel is oxy-combusted in the presence of the separated oxygen [Ahmed, P., Habib, M. A., Ben-Mansour, R., Kirchen, P., Ghoniem, A. F., CFD (computational fluid dynamics) analysis of a novel reactor design using ion transport membranes for oxy-fuel combustion, Energy, 2014, 77, 932-944]. Alternatively, fuel can also be burned in the presence of the separated oxygen and recycled carbon dioxide, in the permeate side of the membrane. Several membrane materials were shown to effectively separate oxygen from a gaseous mixture. Among those, lanthanum cobaltite perovskite ceramics, modified proviskite ceramics [Balachandran, U., Kleefisch, M. S., Kobylinski, T. P., Morissette, S. L., Pei, S Oxygen ion-conducting dense ceramic membranes, US Patent, 1997, 5, 639-437], brownmillerite structured ceramics [Schwartz, M., White, J. H., Sammels, A. F., Solid state oxygen anion and electron mediating membrane and catalytic membrane reactors containing them, US Patent, 2000, 6, 033-632], ceramic metal dual phase membranes [Chen, C. C., Prasad, R., Gottzmann, C. F., Solid electrolyte membrane with porous catalytically-enhancing constituents (assigned to praxair technology), US Patent, 1999, 5, 938-822], and thin duel phase membranes, which consists of chemically stable yttria-stabilized zirconia (YSZ), [Kim, J., Lin, Y. S., Synthesis and oxygen permeation properties of thin YSZ/Pd composite membranes, AIChE Journal, 2000, 46, 1521] have been comprehensively investigated.
In view of the forgoing, one objective of the present invention is to provide a combustion system including an ion transport membrane assembly coupled to an internal combustion engine to generate power via oxy-combusting a fuel stream in a combustion chamber of the internal combustion engine. The ion transport membrane assembly includes a plurality of ion transport membranes, wherein each separates molecular oxygen from a gaseous mixture exposed thereon. Another objective of the present invention is to provide a method of combusting a fuel stream via the combustion system, wherein a portion of an exhaust stream is recycled to sweep the molecular oxygen away from a plurality of permeate zones of the ion transport membrane assembly.